In the field of metal working, it is often necessary to accurately guide a cylindrical member such as a tube or bar, usually of a remarkable length, between feeding means and a machine for working the member, or between a work station and a run-out table, or between the various processing stations of a large scale facility or production line. During processing, the diameter of the cylindrical member may vary, for example, as the cylindrical member is reduced by rolling in passing from one work station to another. Also, in the processing of cylindrical members of varying diameters on the same process line or mill, the problem arises of compulsorily changing the dimensions of the guides along a pass line in which the cylindrical member travels. This problem may not only incur significant down-time of the machine or production line with inherent production losses, but also the requirement of skilled personnel for substituting existing guides with guides of a different diameter to accommodate a cylindrical member of a different diameter.
A plurality of guides are used to support a cylindrical member in a piercer, elongator or straightener portion of a seamless tube mill for the manufacture of elongated seamless tubing. For example, in a seamless tube mill, one of the initial operations is the piercing of a heated or unheated cylindrical metal billet or bar by a pair of angularly disposed driven mill rolls which force the billet or bar over a piercing point on an end of an elongated mandrel bar. Since the billet is rotated by the mill rolls as it is fed over the piercing point, it is accordingly necessary to support the piercing point and the attached elongated mandrel bar for rotation within the rotating billet. The mandrel bar extends away from the mill rolls in the direction of longitudinal movement of the billet over the piercing point for a distance that is at least as great as the length of the longest shell or tube to be formed on the mill. Lengths of upwards of 30 feet are not uncommon. The rear end of the mandrel bar is rotatably supported by a suitable mandrel carriage which is adapted to withdraw the bar from the tube so that the tube can be removed from an outlet table on which it is received after the piercing operation, and then to return the bar to its working position with its piercing point adjacent the mill rolls.
During the piercing operation, a large compressive load is typically exerted on the rotary mandrel bar. In order to support the mandrel bar and prevent it from buckling and vibrating under the high compressive loads as it is rotated during the piercing operation, the bar must be rotatably supported by some type of guide. Moreover, a guide must also rotatably support and steady the pierced portion of the tube having the mandrel passing therethrough as it axially travels away from the piercer rolls.
One type of guide for supporting and containing a mandrel and tube in the piercing segment of a seamless tube mill is a moveable three-roller cluster arrangement disclosed in U.S. Pat. No. 3,101,015 to Schuetz. The three-roller clusters are arranged in spaced-apart stands along the run-out table of the mill. The three-roller support of Schuetz is suitable for use in the piercing segment due to the fact that the elongated mandrel bar remains inside the tube or shell which, in part, prevents the rotating shell from leaving the center of the roller cluster. When the rollers are expanded to accommodate larger diameter tube sizes, the spaces between adjacent rollers become too great to insure 360.degree. tube containment in a mandrelless elongator operation. After the mandrel has been withdrawn, the hollow tube or shell is commonly contained in a box-like enclosure which supports the rotating shape after it is further rolled in the elongator segment of the seamless tube mill.
U.S. Pat. No. 2,104,117 to Findlater discloses a bar guide utilizing two arms having semicircular guide troughs which are longitudinally offset from each other to accommodate various diameter tubes. The guides of Findlater do not offer a wide variety of diameter adjustments or continuous 360.degree. containment in a rotating mandrelless tube operation.
U.S. Pat. No. 2,686,444 to Reichl discloses a roller guide including a plurality of adjacent tube support guide rolls about a longitudinal axis attached to adjustable crank levers. The levers are mounted to a frame and can be variably adjusted. The roller guide of Reichl does not offer 360.degree. containment at larger tube diameters due to one point contact made by each roller guide.
Similar types of mandrel bar steadiers and mandrelless bar steadiers are also required in other types of machines handling tubes. Therefore, while the present invention is particularly suited for use in connection with both the piercing and elongator segments of a seamless tube mill, it is to be understood that the present invention also finds application in other tube making or handling equipment in which a rotating cylindrical member must be supported.
The present invention provides an adjustable guide for supporting a rotating bar or tube, whereby a mandrel bar can be accurately, rotatably held in a desired position with respect to the billet being pierced so that the operation can be carried out without substantial buckling or vibration of the mandrel bar.
More particularly, the present invention provides identical guides for use in both the piercing segment and in the elongator segment of a seamless tube mill whereby the need for the separate roller guides and box enclosures heretofore needed for these mill segments is eliminated. The present invention permits the use of one adjustable guide for operation in both the piercer and elongator segments of a mill to provide a seamless tube mill of substantially reduced size by combining the piercer and elongator segments into one segment.
Another object of the invention is to provide an adjustable guide which allows for the guiding of mandrelless cylindrical members of different diameters in a variety of processing equipment.
A further object of the invention is to provide an adjustable guide for cylindrical members which is of simple construction, easy to use, reliable in operation, as well as relatively economical in cost.